In a concert or studio environment, it is usual to connect sound sources, including guitars and microphones, to amplification equipment with shielded electrical cables. Such cables have a copper core and a metallic shield separated by an insulating material. At each end, a jack or plug, typically ¼ inch (6.35 mm) diameter, allows both the copper core and the shielding of the cable to be electrically connected to electronic circuitry in the relevant electrical equipment. Signals are carried from the sound source in the same form in which they are generated, i.e. as analogue signals in the audible frequency range 20 Hz to 20 kHz. In a studio environment, the same type of cable connects sound sources to mixing desk equipment. Cables used in concert environments can be over 10 m long, although shorter cables tend to be used in studio environments.
Such cables can become internally damaged during use, especially when being used in an on-stage environment, although they may appear externally to be undamaged. Damaged cables cause a reduction in the quality of signals being carried, and may result in unwanted distortion or other degradation of the audio signals. If the core of the cable becomes fractured, the cable can stop functioning altogether, although signal deterioration is more common. The inventor considers that signal degradation might result from fractures in the core and/or shielding and/or from damage to the insulating material separating the core from the shielding resulting in unwanted inductances and/or capacitances, which can cause unwanted resonance and/or filtering when supplied with energy in the form of the audio signals being carried.
The effects of cable damage can be avoided through the use of radio links between the sound source and the mixing desk or amplification equipment. Radio microphones are well known. However, the possibility of radio interference means that digital communication links are more reliable. However, many musicians and sound producers prefer audio signals not to be digitised at any point in their transmission on the basis that this results in a reduction in quality, as well as a less pure sound.
WO2007/031794 discloses arrangements that mitigate these disadvantages. The present invention builds upon the arrangements disclosed in WO2007/031794.